Current Trends of Computer Controlled Machine … Trends of Computer Controlled Machine Centers 1 ....
Transcript of Current Trends of Computer Controlled Machine … Trends of Computer Controlled Machine Centers 1 ....
Presented by
Richard L. Lemaster
Box 8005
NCSU
Raleigh, NC 27695-8005
919-515-1548
Current Trends of Computer Controlled
Machine Centers
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Types of CNC Machine Centers CNC = COMPUTER NUMERIC CONTROLLED
Previously there was a difference – nowadays
that difference is often difficult to determine.
Routers
Point-to-Point
Panel Saws
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Components of CNC Routers CNC = computer numeric controlled
CNC routers come in a variety of sizes, shapes,
configurations, and price.
All routers, however, consist of 3 main components
Mechanicals
Electronics
Software
Will cover the details of each of these components
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CNC Routers
CNC routers range from $2000 systems to units costing
from $500K - $750K.
For years, developers concentrated on making routers
faster, more powerful, and more versatile
Today there is a trend for some manufacturers of routers
to make them easier to use and more affordable
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COMPONENTS OF CNC
MACHINE CENTERS
Mechanics - Base
Electronics
Software
Cast Iron
Steel
Composite resin / aggregate
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MECHANICS - BASE
CAST IRON
high dampening
more expensive
STEEL
cheaper and lighter
not as good dampening
COMPOSITE RESIN / AGGREGATE
new
not as expensive
compromise
easier to setup 10
COMPONENTS OF CNC
MACHINE CENTERS
Mechanics – Drive
Centers
Electronics
Software
Rack and Pinion
Conventional Ball Screw System
“Spin the Nut” System
Linear Motors
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Drive System Options
Rack and Pinion
• least expensive
• not as accurate (more slop)
• prone to dirt contamination
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Drive System Options
Conventional Ball Screw System
• Common system
• Highly accurate
• Prone to screw “whip” at high speeds
• Thicker screw makes too heavy to
move at high speeds
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Drive System Options
“Spin the Nut” System
• For high speed machining
• Allows for heavier non-moving screw
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COMPONENTS OF CNC
MACHINE CENTERS
Mechanics – Spindles
Electronics
Software Steel Bearings vs. Ceramic Bearings
Air Cooled vs. Liquid Cooled
Grease vs. Oil Mist
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What is High Speed?
High speed is a relative term.
CNC Routers
20 years ago: 15,000 rpm, 500 ipm (12 meters / minute)
15 years ago: 30,000 rpm, 1500 ipm (36 meters / minute)
today: 30,000 rpm, 2000+ ipm (48 meters / minute)
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What are the High Speed Spindle Design
Considerations?
• 20,000 rpm steel bearings air cooled grease lubrication
• 30,000 rpm ceramic bearings liquid cooled oil mist lubrication
• 40,000 rpm magnetic bearings – not common in the wood industry since
is so expensive
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COMPONENTS OF CNC
MACHINE CENTERS
Mechanics - Base
Electronics
Software
Types of drive motors
Types of drive controllers
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Drive System Options Drive Motors
Stepper Motors
• cheaper
• slower
• not as accurate (many without feedback positioning)
Servo Motors
• more expensive
• faster
• more accurate 19
Drive System Options Drive Controllers
Hardware Controller • traditionally more common
• propriety based – “closed architecture” (hard to modify or access)
• fast
• more expensive
Computer-Based Controller • cheaper
• slower since goes through computer bus
• “open architecture”
Hybrid Hardware and Computer-Based Controller • good compromise – in speed, open architecture
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COMPONENTS OF CNC
MACHINE CENTERS
Mechanics - Base
Electronics
Software
CAM – computer aided
manufacturing
NBM
Addons
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Mastercam
Mastercam is just one example of a CAM package. It
is the largest seller of a CAM package (base = $5K)
The only difference between MC Mill and MC Router
is Tabs, Nesting, and the Tool Table
ADVANTAGE OF MC (or similar CAM) is that there
are many people trained in it
DISADVANTAGE OF MC is that it is complex and
expensive ($5K)
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NESTED BASED MANUFACTURING
(NBM)
Definition:
Nesting – geometric optimization of part(s) made for a panel
on a CNC router, milling machine, laser, panel saw, etc. for
best yield
NBM – A philosophy which is joined with JIT, cellular
manufacturing, and CAD/CAM
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Two BROAD Types of Router Types
Panel Manufacturing
• cabinets
• book cases
• RTA furniture
• upholstery frames
Stick Manufacturing
• multi part raised panels
• chairs
• 3-D products
Type affects the hold down technique employed 24
Types of Hold Down Techniques
Gaskets
Manual “Flip” Pods Manual Vacuum Pods
Mechanical Fastening (nails)
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Types of Hold Down Techniques
SUMMARY
• Manual “Flip” Pods
• Mechanical Fastening (nails)
• High Vacuum System
• Roller Hold Down
• Manual Vacuum Pods
• Automatic Pods
• Automatic Clamping
• Gaskets
Inexpensive Most Expensive
Most Expensive to Operate
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New “Machine Centers” Robot Machining
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Is gaining popularity due to improvements of
design and control software
Does not cut faster but has quicker moves between cuts
(cheaper than CNC router?)
Basic Design Issues - Machine
Configuration
Fixed Table Cantilever Arm
Fixed table is more stable – cantilever arm is less stable
Allows for larger table and parts 42
Basic Design Issues - Machine
Configuration Column Type With Moving Table
Cantilever arm is less stable
Allows for easily entry of parts 43
Basic Design Issues - Machine
Configuration Fixed Table Gantry Type
Gantry is very stable
Allows for large parts but more difficult loading parts 44
Basic Design Issues - Machine
Configuration Gantry Type Moving Table
Is a probably the most common configuration for all but
those machining very large parts
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HSK - Chuck / Machine Interface
HSK advantages:
highest rotation speeds and torque
transfer
quick change of tool holder
precision centering
Source:
CNC G Code Programming
• Is a way to “manually” program the CNC machine
• Is a “standardized” system (with many machine
dependent commands) though has an ISO standard
• G code – one of many codes, is preparatory in that it
tells the machine what action to take (G00 = rapid move,
G04 = dwell, G90 = absolute programming)
• M code = machine or miscellaneous code (M03 = turn
spindle on CW
• F = feed speed, S = spindle speed, T = tool selection
ALTERNATIVES
Some CNC router manufacturers have developed their
own software
To replace G-code.
Advantages – more intuitive
Disadvantage – not standardized
EXAMPLE – ShopBot
CC = cut circle
M2 = move in x and y direction ie M2 3,4 – move x3, y4
J2 = rapid jog in x and y direction